This invention relates to a method and apparatus for decoding and deriving informational content from multi- frequency signals, and more particularily, in addition to deriving the informational content from those signals the invention relates to method and apparatus for storing signals corresponding to the information contained in the digital signals and selectively retrieving those stored signals.
It has become known in the art to utilize pulse signals having differing frequency contents for the purpose of conveying information and providing operating signals in telecommunications networks and the like. More particularily, it has become known to use such pulses or tone signals for the purpose of conveying numerals selected by a telephone subscriber to a switching system and causing the switching system to be operated to connect the called subscriber indicated by those numerals. While these tone signals are most frequently used for facilitating switching operations, it is quite clear that the generation of combinations of them at a subscriber station can be a way of causing the transmission of information over the same system after completion of a connection in a relatively inexpensive and uncomplicated manner.
It is, therefore, an object of this invention to provide a method and apparatus whereby one party, i.e., a called party, can selectively receive the aforementioned multi-frequency or tone signals following completion of a connection to him, derive informational content from those signals, store signals corresponding with the latter information and selectively retrieve the stored informational signals.
An additional object of the invention is to provide the method and apparatus defined above wherein the multi-frequency signals are received only when desired, such as after a predetermined period of time has elapsed after the connection is completed.
A further object of this invention is to provide a method and apparatus as set forth in the foregoing objects which are capable of being utilized either on a centralized or an individual station basis.